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What is a Water Purifier?

The average consumer probably thinks they know what a water purifier does, but they're probably wrong.  And it's not their fault—the water treatment industry is to blame.

The words "purifier" and "purification" are being abused by people in the industry who should know better. 

As of the date of this post, the top Google result for "methods for purifying water" is a blog post from a franchise for a big name water treatment company entitled "4 Methods to Purify Your Water."  (I won't link them here directly because, shame on them, they don't deserve the traffic.)  The four methods suggested in this article are (1) boiling, (2) filtration, (3) distillation, and (4) chlorination.  While these are all water treatment methods, only one of the four methods mentioned is even capable of producing purified water.

What is purified water?

Many water treatment professionals seem to disagree with me on this point, but I'm going to go ahead and offer a very controversial definition:

A water purifier is a device that produces purified water.

Purified water has a very specific definition according to the United States Pharmacopoeia (USP)

Here are the highlights:

  1. Conductivity no higher than 1.1 µS/cm2 at 20 degrees C (roughly 0.7 PPM TDS)
  2. pH between 5.0 and 7.0.
  3. Bacteria no more than 100 CFU/mL.
  4. A few limits on specific concentrations of certain other impurities.

Most devices that claim to be purifiers do not produce water meeting the USP definition of purified water. 

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Is My Water Filter a Purifier?

Reverse osmosis (RO) is capable of producing purified water under some circumstances, but I have never seen a household single-pass RO system produce water less than 4 PPM TDS (total dissolved solids).  Household RO units typically reduce dissolved solids by 90-95%, so you'd need incoming water with no more than 14 PPM to hit 0.7 PPM treated water TDS.

The very popular Berkey water filter claims to be a "purifier," but also claims to leave the "beneficial" minerals in the water.  It will remove pathogens, but you won't get anywhere near 0.7 PPM TDS.

Boiling can kill pathogens, but it won't reduce the dissolved solids of your water one bit.  Filtration (unless you count RO or ion exchange) won't affect your dissolved solids level significantly.  And chlorination, while a reliable treatment for most pathogens, involves adding more impurities to your water, not removing them.

I am not saying any of these methods are bad.  Household RO is a great way to make your drinking water better if it fits your lifestyle.  I use chlorination every time I fill up my water tanks.  The Berkey water filter is a very popular product, and it's based on solid science.  But it will not produce purified water unless the water you're feeding into it has incredibly low TDS already. 

The only household water treatment device that I've seen that reliably produces purified water is the ZeroWater pitcher.  But it also has a major shortcoming -- it won't remove pathogens, so the water you feed it with must already be microbiologically safe, or it will not meet the USP standard for purified water.

It's Not Lying if You Redefine the Word

Instead of acknowledging that most filters are not purifiers by any rational definition, the water treatment industry has tried to expand the definition of water purification.  Check out Wikipedia's current (as of this writing) definition of water purification:

Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from water. The goal is to produce water fit for a specific purpose.  

With this definition, almost any drinking water treatment system claim to be a purifier.  I could sell you a coffee filter that removes suspended solids with the goal of producing water fit to flush the toilet, and call it a water purifier.  It's absolute nonsense.

Why Does it Matter?

Let's set aside the moral implications of manipulating the definition of a word with the goal of deceiving the public for the sake of marketing.  Do you really need your drinking water to meet the USP definition of purified water?  

In theory, there's no reason why water can't be fit to drink just because it isn't purified.  Water that contains some minerals, is over 7.0 pH, or even more than 100 CFU/mL of non-pathogenic bacteria can be perfectly safe to drink.

In practice, though, it can be difficult to sort out which contaminants are good, which are bad, and which aren't a concern.  Dietary and health needs vary by individual.  Excess sodium or potassium content might be healthy for one individual, but it could contribute to serious health problems in another.  A 30 year old woman starting a family probably cares a lot about things like mercury and lead.  An 80 year old man might not suffer any ill effects from a little excess mercury or lead, but a bout of cryptosporidiosis could kill him.

Purification can be an excessively stringent standard for drinking water, but if you're looking to avoid all harmful impurities, purified water might be what you're looking for.

Know What You're Putting In Your Body

Since both snake oil salesmen and otherwise reputable companies seem willing to abuse the term "purifier," I suggest ignoring that word entirely when purchasing a water treatment device.  Instead, find out specifically what a device is rated to do, how it does it, and what it doesn't do.  Design a water treatment approach that fits your personal needs.

If your water quality is unknown or varied, as is the case for many nomadic and tiny living families, it's important to have a fairly comprehensive water treatment plan.  The good news is that it doesn't cost a lot of money or require a lot of bulky equipment to cover all of your bases.  Check out our suggestions for your lifestyle on our welcome page to get you started.

If you'd like to learn more about water treatment, especially as it relates to small space and nomadic living, stay tuned to this space for some deep dives into specific products, water problems, and strategies for water management in small spaces.  If you have a topic you'd like to hear more about, you can reach me here.

Dan Greatley